posts tagged with the keyword ‘lasercutter’

2014.12.19

I’ve been working on a project that involves stacking of laser cut pieces of wood to create blocks. In theory the laser cutter is a precise CNC machine that has an (almost) negligible kerf. (The kerf is the part that gets cut away. With a saw it’s the width of the saw blade, and you need to account for it.)

Typically I’ve been using this 3mm Baltic Birch plywood from Woodcraft, and it’s been pretty darn close to 3mm, at least within 0.1mm. For most projects this is fine. Even at 3.2mm things will fit together, though perhaps a bit snug. You can always sand things a bit to make them fit.

Stacking presents a new problem though, because the extra height adds up and throws everything off. For the last batch of blocks I assembled I wasn’t aware of the issue, even when the pegs wouldn’t fit. I assumed I screwed up the peg slots, so I just sanded the pegs down a bit until they fit. Even then, they were not the right height in the other direction.

After assembly I noticed that the blocks were different heights than the first batch I created! I went back and measured the sheet of wood and it was 3.4mm. I checked a few more and got ranges between 3.0mm and 3.4mm. The image above shows what happens if you use 3mm wood and 3.3mm wood to construct the same block. At just four layers you’re already off by 1.2mm. For small things that can make a huge difference.

So what’s the solution? I can attempt to sand the sheets before cutting, or partially assemble the blocks and sand them to the proper height before the final step. A colleague suggested getting one large sheet of wood assuming the height would be consistent across one piece. I may try all three solutions, but will probably start with the first, and apply the second solution if required.

So yeah, even with digital fabrication, and laser cutters with almost no kerf… Measure twice so you only have to cut once!

2014.11.28

I needed a single stroke font for some laser cutting. You’d think that would be an easy thing… Well, keep reading.

When laser etching, any font could be used. You can raster etch the type, or “vector etch” the type. Raster etching takes a long time, and vector etching (basically doing a low-power vector “cut”) is fast. If you’re doing 3,000 pieces, the time can make a huge difference!

Here’s a normal font in Inkscape. Fonts consist of an outline which is then filled with a color. In this case, the outline of the font is filled with black and you see what you normally see when viewing a font on a computer screen.

Here’s the normal font with the fill set to none and the stroke (outline) set to a thin line. You could laser etch this (and some people do) but you’re now outlining the letters instead of just etching them with a single stroke. This is fine, but takes more time. Since going really fast is our goal, this doesn’t work.

At this point, you may be thinking “No problem! Our pals at Evil Mad Scientist Laboratories have us covered with Hershey text, and engraving font!” Indeed, Hershey text is awesome, but not always the right solution. I use Hershey text often, and it’s lovely, but let’s keep exploring…

I found these CamBam fonts, which probably work quite well for a spinning bit that is cutting material, but there’s an issue:

All the fonts are built using a 100% overlap in the font design, which tricks my TrueType font design program into thinking they are really looped TrueType fonts, when they really don’t have an inside and outside loop.

A spinning bit cutting material is quite different than a laser cutting material. If you use this font to laser etch, it will double up, which mean you’re lasering the same thing twice. This takes longer, and cuts your material twice. No good.

You can manually go in and delete the overlaps, but it’s a time-consuming pain, and you’ve got better things to do.

I found Machine Tool Gothic, which looks a bit weird when you first select it, but we’ll fix that. Remember that fonts are typically outlines that are filled with a color. That’s what is happening here.

We just need to set the fill to none, and give it a thin stroke. Much better! We’ve nearly got our clean single-stroke engraving font.

Let’s fix the weird lines that connect everything and close the paths. First you’ll want to convert the type to outlines (that’s the “Object to Path” command in Inkscape) and then select the two nodes at each end of the line you want to delete and use the “Delete segment between two non-endpoint nodes” feature to remove the line.

Oh, it’s worth noting that when you convert the type to paths, you lose the ability to edit it as type. More on that later. Here’s the “L” with no extra line connecting everything.

Now, it may look like only certain letters need the extra line deleted, but they all do. Go through each letter to delete the extra lines! If you’re doing a one-off project this may not matter as much, but if we are laser cutting 3,000 pieces, even an extra 5 or 10 seconds per piece will make a huge difference.

Here’s the real reason I wanted to use an editable typeface rather than the Hershey text extension. With text, you can place it on a path. This means you can curve the text onto a circle or some other shape. We want to make sure we’ve got the text exactly as we want it before removing the extra lines. (Remember that we need to change the editable type into outlines before we remove those extra lines.)

Don’t forget to remove the circle, or whatever path you used to place your text on.

Fire up the laser! Here’s our clean and ready to vector-etch single-stroke type.

I started with this letter M, in the typeface Umbra BT. I liked the 3D quality of it, and since I also love using the laser cutter at Milwaukee Makerspace, I had a plan.

The Photoshop mock-up was just an idea, so I re-created the letter M in Inkscape to prepare it to be laser cut. You’ll notice right now that the M in the first image and second image don’t match exactly. (I wish I had noticed at the time!)

I cut the shapes out of 1/8″ Baltic Birch plywood. My plan was to cut one board like this, and I’d the use the pieces to attach to another board, and the template piece as an assembly guide. Good idea, right? Right.

My next thought was, “Why waste full boards to get more pieces?” and I arranged the pieces to minimize waste. This works well for general assembly of things, but for art, maybe not so much. The pieces cut fine, but I did have to deal with kerfs, some scorching, the grain of the wood, etc. None of those things were huge deals, but they’re things to be aware of in the future.

At this point it was just a matter of assembly. A bit of glue, and bit of wood stain, what could go wrong?

There was a lot of time spent with the glue and the clamps. Well, most of the time was spent waiting for glue to dry. I obviously need another 20 spring clamps. Just for fun, this is about the time I got sick and had a work overload, so I started getting really concerned about completing this on time. (It gets worse.)

Here it is done! I call it “M1″ by the way. An “M” for “Milwaukee” or “Mike” or “Mary” or whatever you like… or you could flip it over and make it a “W” for “Wisconsin”, etc.

I also had a nightmare time with the wood stain, though I managed to recover that by changing the piece. I learned everything I’d forgotten about staining wood in the 20 years since I’ve last done it.

Here’s a side view of M1 showing the dimensionality of the piece. The M is about 3/8″ thick.

But wait, what’s that? I still have that leftover piece that I used as an assembly template! Hmmm…

Yeah, here’s “M2″ as it were. I figured that a perfectly nice piece of laser cut wood should not go to waste, so I came up with another idea. I reversed the color scheme of the stains on the two pieces of wood, attached the front piece to a back piece, and blammo! Another wonderful(?) piece of laser cut art.

I think I may actually like M2 better than M1, maybe just because of the process that created it, but hey, you be the judge, or the critic, or the bidder, or whatever. Cheers!

2012.11.11

I made these laser-etched badges at Milwaukee Makerspace recently, and if you’ve see our logo before, you may have noticed it has some thin lines in it. Thin lines are great, except when they aren’t, and when etching with the laser, they might not be.

the photo above shows my three attempts, with the first being on the bottom, and the third being on the top. You can see the difference by comparing the helmet in each badge.

The image above shows our standard helmet logo on the left, and you can see the line widths, which work fine for graphics we use online, or printed materials like flyers and stickers, but for laser etching, the lines are just too thin. The middle logo shows how I tried to fatten up the lines to allow the etching around them to leave a bit more material (in this case 3mm Baltic Birch plywood.) Match the middle logo up with the middle badge in the photo above… it’s better, but still not great.

The logo on the right side shows the lines around the eyes and nose thickened up even more, and this is what worked the best, as seen in the final (top) badge in the top photo. (And yes, these were done using the 60 watt Laser Cutter at Milwaukee Makerspace.)

Here’s a poor macro shot of the second attempt, where you can see that not enough material was left for the eyes and nose, even after the first attempt at fattening up the lines. (I didn’t bother to photograph the first attempt, as I sized up the logo on this, the second attempt, and then maintained the new larger size on the third attempt as well.)

Here’s a poor macro shot of the third attempt, the one with the fattest lines. This one worked out quite well, especially for the eyes and nose. The detail in the solder iron were completely lost, which is fine, as it’s extremely fine detail, and we’re etching it at a small size.

I’m pretty happy with the final result, and I’ll keep in mind that thin lines may need to be fattened up in the future. (There’s always the issue of altering someone’s logo or artwork, but in cases like this it’s necessary if you want good results.) I don’t think there’s any hard and fast rules on this, as things will vary depending on size of artwork, material being etch, and other variables, but it’s a nice reminder that tweaking is needed for this type of thing to work well.

When I first got my Egg-Bot I used an application called “Voronoi Stippler” to play around with stippling, but sadly the code for the application was taken offline. StippleGen2 takes the place of Voronoi Stippler quite well!

Original Hoan Bridge Graphic

I started out with this graphic of the Hoan Bridge, a Milwaukee Landmark, and converted the small color image to a larger grayscale image. (Why the Hoan Bridge? Because someone on Facebook suggested it!)

TSP Artwork

Here is the result of generating the TSP art. What is TSP you ask? Basically, it’s a path with a single line. It’s great for generating toolpaths used by things like CNC machines, engravers, routers, lasers, etc. (Find out more about TSP!)

Stipple Artwork

I wasn’t convinced the TSP art would come out great, so I went to the circular stipples. Here’s the final version, which is incredibly hard to see rendered properly at this size, so look below for some zoomed in versions.

Stipple Artwork Zoomed In

Stipple Artwork Zoomed In More

Stipple Artwork Zoomed In Even More!

As you can see, the circles overlap, which means if we were to etch this with a laser, and use the vector setting (as opposed to raster) it would see each circle as a distinct object, and etch each one. (Etching as raster would most likely just etch it all as one single blob, no individual circles.)

So because each circle will be etched individually, and they overlap, we’ll end up with different heights/layers, as it were, due to some areas of our material being hit with the laser more than once. In other words… texture!

Final Laser-etched piece

Here’s our final piece of laser-etched Baltic Birch plywood. Below you can see some zoomed in shots showing the surface. Notice how the circles are so small they essentially looks like dots. (You can click each photo to see the large version on Flickr.)